Orchard caught her on the second run lap.
"I could hear [from commentary] when I came through on my second lap that she was just behind, so it was 'OK Lizzie's got that' - and I've just got to keep running as best I can and keep in front of Rachel - and I had a good run."
Like many of the athletes at Saturday's race, Backler is heading to Australia for the Xterra Asia Pacific Championships next weekend but hasn't decided if she will take up the offer of a place at the Xterra Worlds in Maui, having been twice before.
"I don't think I perform well in the heat, so I'm not too sure if I will go."
Orchard was delighted with the victory and says it was a long time coming.
"I'm super pleased to have won XTERRA in Rotorua. It's the hometown race and you always want to do well here. I've actually been coming here for over 10 years, starting as a teenager before eventually trying the full triathlon. It's always great, loads of support and so many people cheering you on."
Top Kiwi multisport athlete Braden Currie (Wanaka) successfully defended his pro men's title, crossing the line ahead of Rotorua's Sam Osborne and South Africa's Bradley Weiss.
The 29-year old was neck-and-neck with Osborne out of the swim and into the mountain bike but managed to pull away towards the end of the bike leg.